Introduction to Toxicology

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Introduction to Toxicology

• Richard W. Stair, MD

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Toxicology - Generally Speaking

• 4 million potentially toxic exposures annually
• fewer than 1 reaching hospital are fatal
• if arrive in deep coma, mortality 13-35
• 25 of suicide attempts are via drug OD
• leading fatal exposures analgesics, TCA,
  psychotropics, street drugs, CV agents, alcohols

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Routes of Exposure

• Ingestions 79
• Dermal 7
• Ophthalmologic 6
• Inhalation 5
• Bites and Stings 3
• Injection 0.3

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Initial Assessment - ABCs

• Airway with C spine protection
• Breathing
• Circulation
• Disability
• Exposure

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Toxic History

• Patient story correct about 50
• Remember the Ps
• Paramedics
• parents
• pals
• physicians
• pharmacist

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Toxic History

• AMPLE history
• A age , allergies
• M medications
• P past medical history
• L last meal
• E events leading to condition

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Information Gathering

• Physical Exam
• Poison Control Centers
• Evaluating Toxicity - SATS
• S substance
• A amount
• T time of exposure
• S symptoms
• Diagnostic tests

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Physical Exam - Toxidromes

• Anticholinergic
• Cholinergic
• Sympathomimetic
• Opioid
• Torsion Head and Neck Syndrome
• Phencyclidine Syndrome

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Anticholinergic

• Dry as a bone
• Red as a beet
• Blind as a bat
• Hot as hades
• Mad as a hatter

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Cholinergic

• DUMBELS
• Defecation
• Urination
• Miosis
• Bronchospasm
• Excessive salivation
• Lacrimation
• Seizures

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Sympathomimetic

• Convulsions
• hyperthermia
• tachycardia
• hypertension
• psychosis
• mydriasis
• MIMIC ANTICHOLINERGIC, BUT NOT DRY

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Opioid

• Pinpoint pupil
• Hypoventilation
• Coma
• Hypotension
• Bradycardia
• Hypothermia

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Torsion Head and Neck

• Dysphonia
• Oculogyric Crisis
• Rigidity
• Tremor
• Torticollis

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Phencyclidine

• Miosis
• Rotatory nystagmus
• Combativeness

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Odors as Clues to Toxins

• Acetone acetone, acidosis
• Alcohol not with ethylene glycol
• Bitter Almonds cyanide
• Hemp (burnt rope) marijuana
• Garlic arsenic
• Rotten eggs disulfiram, H2SO4

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7 major mechanisms

• 1. Interfere with O2 transport or utilization
• 2. Depress or stimulate CNS
• 3. Effect on autonomic nervous system
• 4. Effect on lungs
• 5. Effect on heart and vasculature
• 6. Local damage
• 7. Effects liver or kidneys

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Tox Management

• As always, ABCs
• Coma cocktail
• Removal of exposure
• Prevention of Absorption/ Decontamination/
  Enhancement of Elimination
• Antidotes
• Ancillary Tests

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Coma cocktail

• Useful challenge in unresponsive patients
• Consists of glucose, thiamine and naloxone
• Beware of suddenly combative patients
• NOT flumazenil

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Removal of Exposure

• Environmental control
• Removing contaminated clothing
• Removal of pill bottles

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Decontamination

• Many traditional treatments by the wayside
• forced emesis
• lavage
• Must weigh risks and benefits
• Charcoal most commonly used
• limitations

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Charcoal - Why and Why Not

• Why
• adsorption of toxins if early
• prevents toxin from entering circulation
• gut dialysis
• sustained release formulations

• Why Not
• too late
• too risky
• too useless

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Charcoal Doesnt Bind.

• C caustics and corrosives
• H heavy metals
• A alcohols
• R rapidly absorbed/active agents
• C chlorine or iodine
• O others insoluble in water
• A aliphatics and poorly absorbed hydrocarbons
• L laxatives

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Charcoal - Contraindications

• Agents from previous list
• Loss of protective reflexes and/or unstable
• Substances causing rapid depression of
  consciousness or early seizures
• infants less than 6 months
• ingested foreign body
• neurologically impaired
• absent bowel sounds

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But if Charcoal Indicated

• 1g/kg initial dose
• multiple doses for enterohepatic circulation
• digitalis, INH, NSAIDS, phenytoin, salicylates,
  TCA
• multiple doses for gut dialysis
• phenobarbital, dapsone, salicylates, quinine,
  theophylline, carbamazepine

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Whole Bowel Irrigation

• Simply washing out intestines of toxin
• PEG solutions at 2L/hr (40cc/kg/hr)
• Used to remove long acting and sustained release
  preparations, body packers and stuffers, and some
  toxins poorly absorbed by charcoal (ex iron)
• Contraindicated if hematemesis, ileus,
  obstruction, perforation, peritonitis

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Enhanced Elimination

• Alkalinization (no acidification)
• Hemodialysis
• Hemoperfusion

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Antidotes

• Relatively small handful of antidotes for vast
  number of toxins
• Good supportive management first
• See list

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Ancillary testing

• Directed toxicology
• EKG and cardiac monitoring
• Acid base status, osmolar gaps
• CXR if unarouseable or hypoxic

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Safety

• Responsible for safety of patient, other patients
  and families, and staff
• Often have agitation, psychosis, and violence in
  association with toxic exposure or underlying
  psychosocial disorder
• Swift and sure physical restraint
• Judicious use of chemical restraint

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Disposition

• Admission
• Psychiatry
• Home